ADDITIOXAL NOTES ON EVOLUTION. 



By David Tkaii.i,. M.A.. ALB., Ch.M., B.Sc. 



(Abstract.) 



Assuming his previously advanced views* to be true,, 

 namely, that at the birth of organic life the earth's atmosphere 

 contained much carbon dioxide and little or no oxygen, and 

 that the quantity of the former has been gradually diminishing 

 and that of the latter increasing, the author considers the con- 

 clusion inevitable that there must have been a correspondingly 

 slow and steady change in all organisms living in this changing 

 atmosphere. Accordingly he restates the proposition enunciated 

 in the above-mentioned paper with regard to the existence of a 

 regulating centre in every organism. f He lays down, further, 

 that when the interests of the individual conflict with those of 

 the race the greatest good of the greater number determines 

 the issue. In plants, the author remarks, this is exemplified in 

 an individual, for whose growth conditions are favourable, 

 when all its individual needs are met and flower production is 

 not hurried on, but where some check or reminder tliat its 

 individual life is in danger is at once responded to by a stop- 

 page of the growth of leaves and branches and a devotion 

 of all energy to hastening on seed production and the fulfil- 

 ment of its destiny ere it is too late. In animals the author sees 

 an exemplification of his views in the changes that occur in a 

 mother during development of a foetus, the latter, as represent- 

 ing the race, being jealously cared for by the regulating centre 

 even at the expense of the mother who represents merely the 

 individual. 



The author then offers some remarks on the subject of 

 heredity. He considers it agreed that innate or endogenous 

 qualities are transmissible, and as to acquired or exogenous 

 characters, he holds that if these are not inherited there cannot 

 be evolution. To Prof. Thomson's remark, that we do not 

 know of any clear case which would at present warrant the 

 assertion that an acquired modification is ever transmitted from 

 parent to offspring, he replies that the reason of this ignorance 

 lies in the brevity of human experience and its consequent 

 incapacity to measure nature's slow progress during thousands 

 of millions of years. 



* Report S. A. Ass. for Adv. of Science ; Cape Town, 1910, pp. 290-305. 

 t Loc. cit., p. 300. 



